1. Field of the Invention
This invention relates to polyfunctional hexasubstituted benzene derivatives and a method for making polyfunctional hexasubstituted benzene derivatives.
2. Description of the Related Art
Polyfunctional hexasubstituted benzene derivatives known in the art include hexacarboxymethylbenzene [Chem. and Ind., 239 (1964)], hexamethylolbenzene [U.S. Pat. No. 3,362,984], hexamethoxymethylenebenzene, hexa-(2-cyanoethoxy) methylenebenzene, hexaphenoxymethylenebenzene, hexatrimethylsilyloxymethylenebenzene [J. fur Prakt. Chemie 328 (1986)], and triphenyltricarboxybenzene [Chem. Ber., 93, 103 (1960)]. Polyfunctional hexasubstituted benzenes wherein at least 3 of the substituents are saturated carbon chains having 1 to 21 carbon atoms and having hetero functionalities at the end of the carbon chains have not been made.
The cyclotrimerization of simple alkynes to form benzene derivatives has been known in the art since 1866 when it was discovered that benzene can be formed in small amounts by high temperature treatment of acetylene [C. R. Hebd. Seances. Acad. Sci., 905 (1866)]. Over eighty years later, this same cyclization of acetylene to benzene was reported using a homogeneous nickel complex as a catalyst [Liebigs Ann. Chem., 560, 104 (1948)]. Since these original reports, a variety of transition metal complexes have been shown to catalyze the cyclotrimerization of alkynes to substituted benzene derivatives. Such cyclotrimerizations have been accomplished using such complexes as mercury, iron, cobalt, chromium, aluminum-titanium, nickel, palladium, tantalum, niobium, rhodium, ruthenium, and tungsten.
While many transition metals catalyze the reaction, many function only at stoichiometric levels, few provide good yields and even fewer provide good yields when applied to alkyne systems bearing large alkyl substituents. Many of these catalysts do not tolerate polar functional groups such as carboxylic acids, alcohols, and amines well. The only references [J. C. S. Dalton Trans., 2593 (1981) and Chem. Ber., 93, 103 (1960)] on the trimerization of alkynes possessing carboxylic acid functional groups describe conversions of only 11 to 14%. The selectivity of the reaction towards trimerization can also be low, producing linear polymers, tetramers, dimers, as well as several other monomeric and oligomeric by-products.
The use of palladium chloride complexes to catalyze the trimerization of acetylenic hydrocarbons is known [J. Am. Chem. Soc., 92, 2276 (1970)]. A particularly useful catalyst for this reaction is bis(benzonitrile)palladium chloride in a chlorocarbon solvent. This catalyst has been used in the cyclotrimerization of diphenylacetylene, methyl phenylacetylene and 2-butyne. Dimethyl acetylenedicarboxylate has been cyclotrimerized over palladium(0)-on-carbon to give the corresponding hexacarboxymethyl benzene (Chem. and Ind. 239 (1964). A homogeneous palladium chloride catalyst generated from palladium-on-carbon with trimethylsilyl chloride has been used to cyclotrimerize 3-hexyne and 4-decyne [J. Org. Chem., 52, 1161 (1987)].